Figure 4 - available from: Scientific Reports
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Theorical electric field strength overlayed for electrodes in Mid-water (full lines), close to the surface (dashed lines), close to a non-conductive seabed (dashed-dot lines), and close to a conductive seabed (dotted lines) in (a) horizontal plane (Z = −55 cm) and (b) vertical plane Y = 0 cm). Coloured lines represent the magnitude of the electric field (red: 1 Vm-1; cyan: 10 Vm-1); white lines represent the vector field lines for (b) and a projected vector field line on the horizontal plane for (a).
Source publication
Globally, the frequency of shark bites is rising, resulting in an increasing demand for shark deterrents and measures to lessen the impact of shark bites on humans. Most existing shark protection measures are designed to reduce the probability of a bite, but fabrics that minimise injuries when a shark bite occurs can also be used as mitigation devi...
Context in source publication
Context 1
... field modelling. The models show that the electric field propagation was affected by the surface and seabed (Fig. 4). In both planes, the electric fields propagated slightly further when the Scuba7 was close to the surface and the seabed compared to a mid-water situation. For example, 1 Vm −1 was modelled ~1.1 m horizontally from the electrodes in mid-water, but ~1.5 m when close to the non-conductive seabed. However, this difference was not as ...
Citations
... Many of the shark species responsible for human fatalities overlap in their distribution thus, a multi-sensory approach to mitigation is important, as what deters one species may not be effective on another. Accordingly, there is a need to improve other forms of shark mitigation such as electrical shark deterrents (ESDs Thiele et al. 2020), which is likely due to biological factors such as shark size and interspecific differences in their electroreceptors, and general body anatomy and physiology. Better understanding of these differences may allow for the design of more effective types of electric fields and allow more targeted behavioural testing of potential devices in the field. ...
Animals possess a range of sensory systems that are shaped by phylogeny and adapted to their unique life history. The field of sensory ecology studies how animals use these sensory capabilities to acquire and process salient information that enhances survival. Navigation, prey capture, predator avoidance, and communication are behaviours that rely on sensory inputs and are critical to understanding how an animal interacts with the physical environment and the other organisms that share its habitat. Because sensory biology is so critical to the behaviour of an animal, a detailed understanding of a species' sensory capabilities may also reveal novel and potentially more effective ways of manipulating its behaviour for management or conservation purposes. Here we highlight several instances where the application of a sensory ecology approach has been used to tackle challenging conservation problems, with a view to encouraging such an approach in Australian ecosystems. We describe how it is possible to exploit animal sensory systems to control invasive species using sensory traps and reduce negative interactions between humans and animals. We emphasise the importance of understanding and mitigating anthropogenic stressors from the perspective of the animals affected, in both wild animals affected by urban development and captive animals. It is evident that a sensory ecology approach has much to offer in terms of improving animal welfare and the conservation of biodiversity, including through the development of novel technological solutions that augment the current conservation management toolbox.
... In Bahia Honda, anglers who fish with a side-scan sonar or similar commonly used fish finder technology (Cooke et al. 2021) can leverage this technology to monitor for incoming sharks and release fish or can change location to target fish outside of the channel accordingly. Testing potential emerging technological solutions, such as shark deterrent devices (Robbins et al. 2011;O'Connell et al. 2014;Hart and Collin 2015;Kempster et al. 2016;Huveneers et al. 2018;Thiele et al. 2020), could also be promising. These technologies have primarily been developed to reduce shark bycatch or shark bites and should be tested in specific fishery contexts before being marketed as a conservation solution. ...
Objective
Shark depredation, the full or partial consumption of a hooked fish by a shark before it is landed, is an increasing source of human–wildlife conflict in recreational fisheries. Reports of shark depredation in the catch‐and‐release Tarpon (also known as Atlantic Tarpon) Megalops atlanticus fishery in the Florida Keys are increasing, specifically in Bahia Honda, a recreational fishing hot spot and a putative Tarpon prespawning aggregation site.
Methods
Using visual surveys of fishing in Bahia Honda, we quantified depredation rates and drivers of depredation. With acoustic telemetry, we simultaneously tracked 51 Tarpon and 14 Great Hammerheads (also known as Great Hammerhead Sharks) Sphyrna mokarran , the most common shark to depredate Tarpon, to quantify residency and spatial overlap in Bahia Honda.
Result
During the visual survey, 394 Tarpon were hooked. The combined observed shark depredation and immediate postrelease predation rate was 15.3% for Tarpon that were fought longer than 5 min. Survival analysis and decision trees showed that depredation risk was highest in the first 5–12 min of the fight and on the outgoing current. During the spawning season, Great Hammerheads shifted their space use in Bahia Honda to overlap with Tarpon core use areas. Great Hammerheads restricted their space use on the outgoing current when compared to the incoming current, which could drive increased shark–angler interactions.
Conclusion
Bahia Honda has clear ecological importance for both Tarpon and Great Hammerheads as a prespawning aggregation and feeding ground. The observed depredation mortality and postrelease predation mortality raise conservation concerns for the fishery. Efforts to educate anglers to improve best practices, including reducing fight times and ending a fight prematurely when sharks are present, will be essential to increase Tarpon survival and reduce shark–angler conflict.
... For example, personal electric deterrents aim to produce an electric field strong enough to overstimulate a shark's ampullae of Lorenzini, and thus, change the trajectory of the animal. While many of these devices show no evidence of affecting shark behaviour Gauthier et al., 2020), some electric deterrents can reduce the risk of shark bites by ~60 % (Smit and Peddemors, 2003;Huveneers et al., 2013;Kempster et al., 2016;Huveneers et al., 2018;Thiele et al., 2020;Blount et al., 2021;Riley et al., 2022b). Modelling has predicted that across Australia, >1000 people could potentially avoid being bitten by 2066 if all water-users wore effective personal shark deterrents (Bradshaw et al., 2021). ...
... Modelling has predicted that across Australia, >1000 people could potentially avoid being bitten by 2066 if all water-users wore effective personal shark deterrents (Bradshaw et al., 2021). However, the range of these deterrents is typically limited (i.e., when sharks are within ~1 m) and sharks will consume baits located between the device's electrodes Gauthier et al., 2020;Smit and Peddemors, 2003;Thiele et al., 2020). 3. Prevent bleeding; reduce injuries from shark bites when sharks cannot be deterred -The aim is to reduce injuries and recovery times when a bite occurs. ...
... 3. Prevent bleeding; reduce injuries from shark bites when sharks cannot be deterred -The aim is to reduce injuries and recovery times when a bite occurs. This can be achieved by wearing novel puncture-and tear-proof wetsuits (Whitmarsh et al., 2019;Thiele et al., 2020) or by applying suitable first aid (Tucker et al., 2022). While crushing injuries, skin punctures, and lacerations are still possible, these protective wetsuits can help reduce blood loss, providing more time for medical aid to be given to the victim. ...
Shark-human interactions are some of the most pervasive human-wildlife conflicts, and their frequencies are increasing globally. New South Wales (Australia) was the first to implement a broad-scale program of shark-bite mitigation in 1937 using shark nets, which expanded in the late 2010s to include non-lethal measures. Using 196 unprovoked shark-human interactions recorded in New South Wales since 1900, we show that bites shifted from being predominantly on swimmers to 79 % on surfers by the 1980s and increased 2–4-fold. We could not detect differences in the interaction rate at netted versus non-netted beaches since the 2000s, partly because of low incidence and high variance. Although shark-human interactions continued to occur at beaches with tagged-shark listening stations, there were no interactions while SMART drumlines and/or drones were deployed. Our effect-size analyses show that a small increase in the difference between mitigated and non-mitigated beaches could indicate reductions in shark-human interactions. Area-based protection alone is insufficient to reduce shark-human interactions, so we propose a new, globally transferable approach to minimise risk of shark bite more effectively.
... Magnets have been successful in some applications to deter elasmobranchs Richards et al., 2018), but in many cases their effectiveness is mixed (Robbins et al., 2011) or negligible (Godin et al., 2013;Huveneers et al., 2018). As a result, the field has shifted to the use of electric deterrents with a higher deterrent success rate and a wider area of effect (Egeberg et al., 2019;Gauthier et al., 2020;Huveneers et al., 2013;Thiele et al., 2020). Though evidence supports a broader adoption of electroderrents, for permanent fixtures like oyster leases they can be less practical than permanent magnets since they must be powered constantly and are more costly to purchase. ...
Cultured oysters are one of the most valuable marine industries globally, however, predation of oysters during the grow out phase by rays can lead to large crop losses. Ray predation is usually mitigated by building large, netted structures around or over oyster racks, but these can fail, are costly to maintain, and can lead to parasitic flatworms that lower oyster value. Here we examine the potential of using non-lethal deterrents including magnets and electric deterrents to reduce oyster predation from six species of rays. A preliminary field experiment compared the deterrent potential of ferrite, rare earth (neodymium) and an electric deterrent, and found only the electric deterrent reliably prevented rays from feeding on baits (100% of interactions with rays). A larger experiment conducted amongst oyster farms found the electric deterrent was very effective (85.48% across all interactions) at reducing feeding interactions relative to a control. These results highlight that electric deterrents could be developed to reduce oyster predation by rays without the limitations of more traditional measures. Furthermore, permanent magnets were considerably less effective at deterring batoid interactions than electric deterrents, and would not be viable for these applications.
... Furthermore, faeces evacuation was performed not in front of a cage with divers but a distance from a shark cage. Blacktip shark, Carcharhinus melanopterus, exhibited a tail flick, muscle spasm, head shake, and a fast direction change when the electrodes were energized when 10 cm from their snouts in a field experiment (Thiel et al., 2020). The white shark was too far from the shark cage, which does produce a small near field electrical potential but not near the high voltage applied in the experiment, to respond with such a manner. ...
In this short note, we describe the convulsive body shuddering of a white shark as it approached two large metallic shark cages, each with multiple divers standing within them. When animals feel threatened, they experience conflicting instincts — one is to escape and another is to fight. In this situation, they do not always fight but often perform an agonistic, or aggressive display. Having arrived at the source of an olfactory corridor, this white shark was confronted with highly visible cages made with aluminium bars. The divers use hookah air hoses to breathe, and were therefore releasing bubbles, which reflect light and generate sounds as they oscillate toward the surface. The photographers may also have been taking pictures of the shark with their flash-bulb equipped cameras, which produce a sudden disruptive flash of irradiance. The shark’s behaviour is illustrated with a series of video frames as he approaches the cage. The body of the shark shutters convulsively and he opens his mouth, keeping it open for a prolonged period of 2.8 s as he passes close to the cage, while (1) depressing his pectoral fins, (2) hunching his back, (3) keeping his caudal fin held at right angle to the axis of view to increase his apparent size, and (4) shaking his body with spasmodic oscillations. The shark appears frightened, and hence may perform the display to discourage any aggression directed at him by the cage with humans emitting a panoply of frightening stimuli. Alternative explanations of the motivation behind this behaviour are also discussed. We hope that it will lead other scientists to look for this behaviour when observing the behaviour of white sharks from a cage, so they can provide further evidence shedding light upon the shark’s motivation for performing this conspicuous behaviour.
... Past studies have tested deterrents using static baits; however, it must be considered that the stimulus for a shark to depredate a struggling hooked fish is likely to be stronger than feeding on static bait, so the potential effectiveness of deterrents for reducing depredation may be lower than when static bait is used. There has also been significant work investigating the effectiveness of personal electrical shark deterrents for ocean users, such as surfers and divers (Gauthier et al. 2020;Huveneers et al. 2018;Marcotte and Lowe 2008;Thiele et al. 2020). Only recently has this technology been adapted in the development of deterrents for use in recreational fisheries, with a single study investigating their effectiveness. ...
Shark depredation is a complex social-ecological issue that affects a range of fisheries worldwide. Increasing concern about the impacts of shark depredation, and how it intersects with the broader context of fisheries management, has driven recent research in this area, especially in Australia and the United States. This review synthesises these recent advances and provides strategic guidance for researchers aiming to characterise the occurrence of depredation, identify the shark species responsible, and test deterrent and management approaches to reduce its impacts. Specifically, the review covers the application of social science approaches, as well as advances in video camera and genetic methods for identifying depredating species. The practicalities and considerations for testing magnetic, electrical, and acoustic deterrent devices are discussed in light of recent research. Key concepts for the management of shark depredation are reviewed, with recommendations made to guide future research and policy development. Specific management responses to address shark depredation are lacking, and this review emphasizes that a “silver bullet” approach for mitigating depredation does not yet exist. Rather, future efforts to manage shark depredation must rely on a diverse range of integrated approaches involving those in the fishery (fishers, scientists and fishery managers), social scientists, educators, and other stakeholders.
... For example, personal electric deterrents aim to produce an electric field strong enough to overstimulate a shark's ampullae of Lorenzini and thus change the trajectory of the animal. While many of these devices show no evidence of affecting shark behaviour (Huveneers et al., 2018b;Gauthier et al., 2020), some electric deterrents can reduce the risk of shark bites by ∼60% Kempster et al., 2016;Huveneers et al., 2018b;Thiele et al., 2020). However, even when reactions are observed, the range of the effect is typically limited (when sharks are within ∼1 m of the target) and many sharks still consume baits located between the device's electrodes during field testing of personal deterrents (Gauthier et al., 2020;Thiele et al., 2020). ...
... While many of these devices show no evidence of affecting shark behaviour (Huveneers et al., 2018b;Gauthier et al., 2020), some electric deterrents can reduce the risk of shark bites by ∼60% Kempster et al., 2016;Huveneers et al., 2018b;Thiele et al., 2020). However, even when reactions are observed, the range of the effect is typically limited (when sharks are within ∼1 m of the target) and many sharks still consume baits located between the device's electrodes during field testing of personal deterrents (Gauthier et al., 2020;Thiele et al., 2020). ...
... However, stereo-cameras are expensive and time-consuming because they require frequent calibration and post-trial video processing using proprietary software to estimate distance (Langlois et al., 2020). However, some studies have used experienced observers to estimate distances instead of stereocameras Thiele et al., 2020). While visually estimating distances is not as time-consuming and more logistically feasible, it is unknown whether visual estimates produce biased or more uncertain estimates relative to stereo-cameras. ...
While personal electric deterrents can reduce the risk of shark bites, evidence for the efficacy of other products is limited. We assessed two versions of a novel electric deterrent-80 and 150 volts (V)-designed to protect a large area (8 m deep × 6 m wide) or to be linked together for greater spatial coverage. We did 116 experimental trials on 43 white sharks (Carcharodon carcharias) to assess: (a) percentage of baits taken; (b) distance between bait and shark; (c) number of passes; and (d) whether sharks reacted to the deterrent. The proportion of baits taken was reduced by 24% (80 V) and 48% (150 V), although the high variance of the effect coefficient precluded statistical differentiation. Only the 150-V deterrent increased the distance between bait and shark (control: 1.59 ± 0.28 m versus active deterrent: 3.33 ± 0.33 m), but both versions increased the likelihood of a reaction (average reaction distance: 1.88 ± 0.14 m). Results were similar whether we measured distances using stereo-cameras or estimated them in situ, suggesting that stereo-cameras might not be necessary to quantify distances between sharks and baits. Our findings provide more evidence that electric deterrents can reduce the risk of shark bite, but the restricted efficacy limits the suitability of this device.
... These animals are considerably resilient to anthropogenic-induced stressors; for example, capture of up to 75 min on SMART drumlines, followed by acoustic tagging and muscle biopsies and blood draws does not lead to physiological impairment or mortality (Gallagher et al. 2019;Tate et al. 2019). With regards to the deterrent trials, the devices tested have either had no effects (Huveneers et al. 2018b) or have a very small range of less than 2 m (Gauthier et al. 2020;Thiele et al. 2020). Therefore, we would not have expected sampling or deterrent testing to lead white sharks to leave the Neptune Islands. ...
Context. Researchers studying animals need to ensure that sampling procedures and the methods they use are as harmless and non-disruptive as possible, particularly when their focal species are threatened or protected. White sharks (Carcharodon carcharias) are Vulnerable under the IUCN Red List, protected globally, and are frequently studied by marine ecologists. Aims. To assess white shark responses to research activities (i.e. tagging and biopsy procedures, and electric deterrent trials) conducted at the Neptune Islands Group Marine Park (South Australia, Australia). Methods. Trends in shark residency following research activities were assessed by comparing shark abundance (number of sharks detected by acoustic receivers and sighted by cage-diving operators) before, during, and after scientific expeditions, and to natural fluctuations in the absence of research activities using 8 years (2013–2021) of acoustic tracking and daily sighting reports from a wildlife tourism industry. Key results. Number of white sharks and residency decreased after sampling. However, changes observed following research activities were similar to natural fluctuations, suggesting that these changes reflected natural variations rather than being due to sharks responding negatively to the research activities. Conclusions. Our study showed that external tagging, biopsies, or deterrent trials do not affect short- and long-term residency or abundance of white sharks, probably owing to the research activities being minimally intrusive and to sharks having efficient immune systems and remarkable ability to heal from injuries. Implications. Re-evaluating study methods forms part of the researcher’s responsibilities to ensure best practice and to abide by national and international codes for the care and use of animals for scientific purposes.
... www.nature.com/scientificdata/ potentially result in higher survival rates of the user if the fabric is concentrated around the torso region 30,31 . Redesigning data acquisition and entry process to allow for categorical columns permits these types of analyses. ...
We describe the Australian Shark-Incident Database, formerly known as the Australian Shark-Attack File, which contains comprehensive reports of 1,196 shark bites that have occurred in Australia over 231 years (1791–2022). Data were collated by the Taronga Conservation Society Australia using purpose designed questionnaires provided to shark-bite victims or witnesses, media reports, and information provided by the department responsible for fisheries in each Australian state (including the Northern Territory). The dataset includes provoked and unprovoked bites from fresh, brackish, and marine waters in Australia. Data span 22 suspected shark species. This dataset will be publicly available, and can be used by analysts to decipher environmental, biological, and social patterns of shark bites in Australia. The information will aid scientists, conservationists, authorities, and members of the public to make informed decisions when implementing or selecting mitigation measures.
... Although a number of shark deterrents have been developed for use in recreational fishing, including electrical [57] and magnetic [58] devices, other deterrents are being developed [59]. Consideration is also being given to modification of shark deterrent products developed for swimmers, divers and surfers, which can be cost effective, but require further development for recreational fishing especially given that the effectiveness of those deterrents vary considerably [60][61][62][63]. In the absence of affordable and effective deterrent devices, fishers will need to continue to modify their behaviour to mitigate depredation. ...
The loss of hooked fish from shark depredation has become an increasing problem in marine recreational fisheries worldwide, particularly among charter and private-boat recreational fishers. There is growing need to understand the prevalence of shark encounters, where depredation occurs and how recreational fishers respond to and mitigate depredation. This study of 1340 charter and private-boat recreational fishers in north-western Australia, included both probability-based (telephone and online) and opt-in (online) survey methods and is the first to document mitigation methods used by recreational fishers. More than half of the respondents (728) who completed the survey indicated that they had attempted to mitigate depredation. In the probability-based survey, the main mitigation methods reported by charter and private-boat fishers were to move spots, use wire trace or stop fishing. Depredation evokes strong opinions from some sections of the fishing population. Although more avid fishers self-selected for the opt-in surveys, the inclusion of information from these respondents, particularly from open-ended questions, provided detailed information on attitudes among fishers where this issue is of concern. This study highlights the wide range of views and concerns regarding depredation, all of which need to be considered when developing policies and guidelines around this issue. As with other contentious issues where changes in fishing behaviour are required, decision-makers will need to devise strategies to inform and educate the fishing public in how to mitigate against depredation.
